This application claims the benefit of Japanese Patent applications Nos. 11-020827 and 11-341663 which are hereby incorporated by reference.
1. Field of the Invention
This invention relates to a stereomicroscope, in particular, to a parallel type (hereinafter referred to as Galileo type) stereomicroscope and to an objective lens used for it.
2. Related Background Art
FIG. 8 shows an optical system of a Galileo type stereomicroscope according to prior art. In the Galileo type stereomicroscope, images of an object for left optical path and right optical path are formed at infinity by an objective lens 2 used in common with left and right optical paths. A focal variable magnification lenses 3a and 3b independently arranged in the left and right optical paths, respectively, vary magnifications of both light paths. Then, imaging lenses 4a and 4b independently arranged in the left and right optical paths form images of the object at left and right image planes 5a and 5b, respectively. Finally, the images are observed through left and right eyepieces 6a and 6b, respectively.
At this time, an eye-level, which corresponds to the height between the object plane and the eyepoint of the eyepiece 6a (or 6b), is fixed in the Galileo type stereomicroscope according to prior art. When plurality of observer with difference in their physique use the same stereomicroscope, an observer having a physique not suitable for this stereomicroscope is compelled to keep observation in a forced posture. Therefore, there is a defect that this stereomicroscope is not suitable for long observation.
In order to solve the defect, it is necessary to make the distance D23 in FIG. 8 variable. If this method is applied to an objective lens for a Galileo type stereomicroscope according to prior art, a large amount of coma is produced in a periphery of an image field. As a result, image quality in the periphery of the image field is severely degraded. Therefore, this becomes another defect.
The present invention was conceived taking the above-mentioned problems into consideration. An object of the present invention is to provide a Galileo type stereomicroscope capable of adjusting an eye-level at observer""s desire, and an objective lens keeping small change in aberration and keeping good imaging quality up to a periphery of an image field while the eye-level is changed.
The Galileo type stereomicroscope of the present invention comprises; an objective lens (2), a pair of a focal variable magnification lenses (3a, 3b), a pair of imaging lenses (4a, 4b), and a pair of eyepiece lenses (6a, 6b) are arranged in order from an object side, wherein said objective lens (2), said pair of a focal variable magnification lenses (3a, 3b), said pair of imaging lenses (4a, 4b) and said pair of eyepiece lenses (6a, 6b) are moved in a body (integrally) relative to an microscope holder (13, 14, 15), and a space between said objective lens and said pair of a focal variable magnification lenses can be adjustable.
In the Galileo type stereomicroscope according to the present invention, the adjustment of said space is performed by moving said objective lens while said pair of a focal variable magnification lenses are fixed relative to said microscope holder.
In the Galileo type stereomicroscope according to the present invention, the adjustment of said space is performed by moving said pair of a focal variable magnification lenses while said objective lens is fixed relative to said microscope holder.
In the Galileo type stereomicroscope according to the present invention, the stereomicroscope has an eye-level being variable without changing the focusing position by varying a space between an objective lens (2) and a pair of a focal variable magnification lenses (3a, 3b), wherein a variable amount Z of said eye-level satisfies the following condition;
Z greater than f0/3
where f0 denotes a focal length of the objective lens to be used.
In the Galileo type stereomicroscope according to the present invention, the stereomicroscope comprises, in order from the image side, a first lens group having a positive refractive power comprising a positive meniscus lens, which is disposed closest to the image, facing the convex surface to the image side, a second lens group having a negative refractive power comprising a negative lens facing a strong concave surface to the object side, and a third lens group having a positive refractive power